| Abstrakt: |
The oxygen-stable isotope mass-independent composition (Δ(17O) = d(17O) - 0.52×d(18O)) has proven to be a robust tool for probing photochemical cycling and atmospheric formation pathways of oxidized reactive nitrogen (NOy). Several studies have developed modeling techniques to implicitly model Δ(17O) based on numerous assumptions that may not always be valid. Thus, these models may be oversimplified and limit our ability to compare model Δ(17O) values of NOy with observations. In this work, we introduce a 5 novel method for explicit tracking of O3 transfer and propagation into NOy and odd oxygen (Ox), integrated into the Regional Atmospheric Chemistry Mechanism, version 2 (RACM2). Termed ICOIN-RACM2 (InCorporating Oxygen Isotopes of NOy in RACM2), this new model includes the addition of 55 new species and 727 replicate reactions to represent the oxygen isotopologues of NOy and Ox. Employing this mechanism within a box model, we simulate Δ(17O) for various NOy and Ox molecules for chamber experiments with varying initial nitrogen oxides (NOx = NO + NO2) and a-pinene conditions, revealing response shifts in Δ(17O) linked to distinct oxidant conditions. Furthermore, diel cycles are simulated under two summertime scenarios, representative of an urban and rural site, revealing pronounced Δ(17O) diurnal patterns for several NOy components and substantial Δ(17O) differences associated with pollution levels (urban vs. rural). Overall, the proposed mechanism offers the potential to assess NOy oxidation chemistry in chamber studies and air quality campaigns through Δ(17O) model comparisons against observations. The integration of this mechanism into a 3-D atmospheric chemistry transport model is expected to notably enhance our capacity to model and anticipate Δ(17O) across landscapes, consequently refining model representations of atmospheric chemistry and tropospheric oxidation capacity. [ABSTRACT FROM AUTHOR] |
